组织多普勒超声应用

Current Applications of Tissue Doppler Imaging李道輿醫師高雄榮民總醫院Tissue Doppler imaging (TDI) is a relatively new echocardiographic technique that uses Doppler principles to measure the velocity of myocardial motion. We describe the principles behind and the clinical utility of TDI.Principles of TDIDoppler echocardiography relies on detection of the shift in frequency of ultrasound signals reflected from moving objects. With this principle, conventional Doppler techniques assess the velocity of blood flow by measuring high-frequency, low-amplitude signals from small, fast-moving blood cells. In TDI, the same Doppler principles are used to quantify the higher-amplitude, lower-velocity signals of myocardial tissue motion.There are important limitations to TD interrogation. As with all Doppler techniques, TDI measures only the vector of motion that is parallel to the direction of the ultrasound beam. In addition, TDI measures absolute tissue velocity and is unable to discriminate passive motion (related to translation or tethering) from active motion (fiber shortening or lengthening). The emerging technology of Doppler strain imaging provides a means to differentiate true contractility from passive myocardial motion by looking at relative changes in tissue velocity.TDI can be performed in pulsed-wave and color modes. Pulsed-wave TDI is used to measure peak myocardial velocities and is particularly well suited to the measurement of long-axis ventricular motion because the longitudinally oriented endocardial fibers are most parallel to the ultrasound beam in the apical views. Because the apex remains relatively stationary throughout the cardiac cycle,mitral annular motion is a good surrogate measure of overall longitudinal left ventricular (LV) contraction and relaxation.To measure longitudinal myocardial velocities, the sample volume is placed in the ventricular myocardium immediately adjacent to the mitral annulus. The cardiac cycle is represented by 3 waveforms (Figure 1): (1) Sa, systolic myocardial velocity above the baseline as the annulus descends toward the apex;(2) Ea, early diastolic myocardial relaxation velocity below the baseline as the annulus ascends away from the apex; and (3) Aa, myocardial velocity associated with atrial contraction. The lower-case “a” for annulus or “m” for myocardial (Ea or Em) and the superscripted prime symbol (E') are used to differentiate tissue Doppler velocities from conventional mitral inflow. Pulsed-wave TDI has high temporal resolution but does not permit simultaneous analysis of multiple myocardial segments.Figure 1With color TDI, a color-coded representation of myocardial velocities is superimposed on gray-scale 2-dimensional or M-mode images to indicate the direction and velocity of myocardial motion. Color TDI mode has the advantage of increased spatial resolution and the ability to evaluate multiple structures andsegments in a single view.Clinical Applications of TDIAssessment of LV Systolic FunctionSystolic myocardial velocity (Sa) at the lateral mitral annulus is a measure of longitudinal systolic function and is correlated with measurements of LV ejection fraction and peak dP/dt. A reduction in Sa velocity can be detected within 15 seconds of the onset of ischemia, and regional reductions in Sa are correlated with regional wall-motion abnormalities. Incorporation of TDI measures of systolic function in exercise testing to assess for ischemia, viability, and contractile reserve has been suggested because peak Sa velocity normally increases with dobutamine infusion and exercise and decreases with ischemia. The technical difficulties of timely acquisition of both 2-dimensional and TDI data during exercise represent the major limitations to routine integration in stress testing.Assessment of Diastolic FunctionTraditional echocardiographic assessment of LV diastolic function relied on Doppler patterns of mitral inflow. Reflecting the pressure gradient between the left atrium and LV, transmitral velocities are directly related to left atrial pressure (preload) and independently and inversely related to ventricular relaxation. Because mitral inflow patterns are highly sensitive to preload and can change dramatically as diastolic dysfunction progresses, the use of mitral valve inflow patterns to assess diastolic function remains limited.TDI assessment of diastolic function is less load dependent than that provided by standard Doppler techniques. Ea reflects the velocity of early myocardial relaxation as the mitral annulus ascends during early rapid LV filling. Peak Ea velocity can be measured from any aspect of the mitral annulus from the apical views, with the lateral annulus most commonly used. Because of intrinsic differences in myocardial fiber orientation, septal Ea velocities are slightly lowerthan lateral Ea velocities.Validated against invasive hemodynamic measures, TDI can be correlated with [tau], the time constant of isovolumic relaxation. Lateral Ea velocities can be 20 cm/s or higher in children and healthy young adults, but these values decline with age. In adults >30 years old, a lateral Ea velocity >12 cm/s is associated with normal LV diastolic function. Reductions in lateral Ea velocity to <=8 cm/s in middle-aged to older adults indicate impaired LV relaxation and can assist in differentiating a normal from a pseudonormal mitral inflow pattern. Unlike conventional mitral inflow patterns, Ea is resistant to changes in filling pressure, although preload dependence is more pronounced in structurally normal hearts.Novel Applications of TDIA number of emerging applications for TDI are under active investigation. Estimation of LV Filling PressuresSimultaneous cardiac catheterization and echocardiographic studies have shown that LV filling pressures are correlated with the ratio of the mitral inflow E wave to the tissue Doppler Ea wave (E/Ea). This relation is based on Ea velocities that “correct” E-wave velocities for the impact of relaxation. The E/Ea ratio can be used to estimate LV filling pressures as follows: E/lateral Ea>10 or E/septal Ea>15 is correlated with an elevated LV end-diastolic pressure, and E/Ea<8 is correlated with a normal LV end-diastolic pressure.Differentiation Between Constrictive and Restrictive PhysiologyBoth constrictive pericarditis and restrictive cardiomyopathy are associated with abnormal LV filling. With constrictive physiology, pericardial constraint impedes normal filling. In the absence of myocardial disease, Ea velocities typically remain normal. In contrast, the intrinsic myocardial abnormalities characteristic of restrictive cardiomyopathy result in impaired relaxation and reduced Ea velocities.Early Diagnosis of Genetic DiseaseAlthough unexplained LV hypertrophy is typically required to diagnose hypertrophic cardiomyopathy (HCM), the degree of hypertrophy and age of onset are highly variable. Abnormalities of diastolic function, as reflected by a reduction of Ea velocities, are present in individuals who have inherited a sarcomere gene mutation before the development of LV hypertrophy. Reduced Ea velocities have been similarly demonstrated in patients in the early stages of Fabry disease.Differentiation of Athlete's Heart From HCMApproximately 2% of elite athletes may have an abnormal degree of LV hypertrophy.15 Discriminating physiological hypertrophy due to intense athletic conditioning from pathological hypertrophy can be challenging. Athletes typically have highly compliant ventricles with brisk Ea velocities, in contrast to the reduced Ea velocities in individuals with HCM.Assessment of Cardiac DyssynchronyIdentifying patients who will benefit from cardiac resynchronization therapy, which can improve heart failure morbidity and mortality rates, has been challenging. TDI can be used to assess the relative timing of peak systolic contraction in multiple myocardial regions. The standard deviation of the time to peak contraction represents a measure of overall ventricular synchrony and may help identify potential responders to cardiac resynchronization therapy. Assessment of Right Ventricular FunctionThe complexity of right ventricular anatomy and geometry challenges accurate assessment of right ventricular systolic function, an important prognostic indicator in patients with heart failure and in postinfarction patients. Reduced tricuspid annular velocities with TDI have been documented in a variety of disease settings, including postinferior myocardial infarction, chronic pulmonary hypertension, and chronic heart failure.Cardiac Resynchronization Therapy (CRT)Hsin-Yueh Liang MDChina Medical University HospitalMay 2007Heart Failure with DyssynchronySynchronization after CRTClinical Benefits of CRTz453 patients with moderate to severe HFEF ≤35%, QRS ≥ 130 msz After 6 months1. The distance walked in 6 min2. Functional class3. Quality of life4. Time on the treadmill during exercise testing5. Ejection fraction6. HospitalizationAHA/ACC guideline for CRTLimitations of Wide QRS as Patient Selection Criteria for CRTz Non-responders of CRT are common: about 1/3 of patientsz LBBB vs IVCD vs RBBB: RBBB responders less favorable to CRT (MIRACLE data)z Patients with QRS of 120-150 ms respond less than with QRS> 150 ms Which Echo technique?z M-modez Pulsed-wave TDIz Color-coded TDIz TSIz Strainz 3 DSPWMD M-modez130 msPulsed-wave TDIz60 msColor-coded TDI 2 segsz65 msColor-coded TDI 12 segsz100 msTissue Synchronization ImagingStrain4DAcknowledgmentz Theodore Abraham M.D, Johns Hopkins University, Baltimore, MD, USAz周湘台教授中國附醫z李智雄醫師高醫附醫z林慶正醫師高醫附醫z Anne Capriotti, Johns Hopkins University, Baltimore, MD, USAz Roman Chojnowski, Johns Hopkins University Hospital, Baltimore, MD, USATEE Guide in the Deployment of ASD OccluderDevice林維文臺中榮民總醫院心臟血管中心Atrial septal defect (ASD) is a common form of congenital heart disease accounting for approximately 10% of all congenital cardiac defects. It is caused by the failure of a part of the atrial septum to close completely during the development of the heart. ASD can be divided into several different types, including secundum, primum and sinus venosus type. Twenty percent of atrial septal defects will close spontaneously in the first year of life. One percent become symptomatic in the first year, with an associated 0.1% mortality. There is a 25% lifetime risk of mortality in unrepaired atrial septal defects. Certain types of ASD's (sinus venosus and primum varieties) have no chance of spontaneous closure, and patients with these types of ASD's are not candidates for transcatheter closure because of the location of the ASD. Open heart surgery is indicated for patients with these types of ASD's. Surgical closure of ASD has been practiced for more than 45 years, and has been considered the standard treatment for patients. Transcatheter closure of secundum ASD has evolved over the past three decades, and is being increasingly used in recent years. The Amplatzer septal occluder (ASO) is the most commonly used devices, due to it is safe and easy to use with a high success rate. Using echocardiography to carefully select certain subgroup of patient is important. It include secundum ASD (diameter less than 30 mm), a left-to-right shunt with a Qp/Qs ratio of .5:1 or the presence of right ventricular volume overload, the presence of a distance of greater than 5 mm from the margins of the ASD to the coronary sinus, atrioventricular valves and right upper pulmonary vein. Patient received anesthesia with transesophageal echocardiography (TEE) monitor was used inour early series. Intracardiac echocardiography (ICE) without generalized anesthesia is used in our patients. Live 3D transthoracic echocardiography (TTE), although does not need anesthesia, had several significant limitation, including low frame rate, poor spatial and temporal resolution. In our limited experience, transcatheter closure of secundum ASD using the ASO is a safe and effective alternative to surgical repair, with a good immediate results, but long term follow up is necessary. Appropriate patient selection is the most important factor for successful device closure.Clinical Application of Real-time 3DEchocardiography蔡惟全Assistant Professor of MedicineNational Cheng Kung University Medical CenterThe concept of 3D echocardiography is not new. Dynamic 3D cardiac image could be obtained from acquiring 2D imaging and reconstructed using an off-line process previously. Recently, 3D echocardiography can be acquired “live” by using a newly developed matrix array probe. However, clinical applications of real-time 3D echocardiography (RT3D ECHO) are not well established.The potential advantages in clinical applications of RT3D ECHO include 1) better imaging and locating cardiac structure changes; 2) improved cardiac quantification; 3) providing therapeutic applications.(1)Better imaging and locating cardiac structure changes: Using 2Dechocardiography, it was difficult to locate the exact area of abnormalities.One of the immediate impacts of RT3D ECHO is that provides an accurate “surgical view” of the heart prior to surgery through the enhanced ability to identify and pinpoint the exact locations of abnormalities.(2)Improved cardiac quantification: RT3D ECHO is a much better option thanother imaging methods for left ventricular volume assessment as it enables clinicians to measure without making geometric assumptions.(3)Providing therapeutic applications: RT3D ECHO has been used in guidingmyocardium biopsy, localization of catheter ablation, and monitoring of ASD occlusion.From more data from clinical practice and research, RT3D ECHO can be extended to more aspects for patient care. RT3D ECHO is a significant new advancement in echocardiography.。